Adaptive gain adjustment control

ABSTRACT

Systems and techniques are disclosed relating to telecommunications which include transmitting a plurality of data groups to a receiver at a first power level, retransmitting a first one of the data groups to the receiver at a second power level lower than the first power level, providing feedback from the receiver relating to the retransmission of the first one of the data groups, and retransmitting a second one of the data groups to the receiver at a third power level different from the second power level, the third power level being a function of the feedback. It is emphasized that this abstract is provided to comply with the rules requiring an abstract which will allow a searcher or other reader to quickly ascertain the subject matter of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or the meaning of the claims.

CLAIM OF PRIORITY UNDER 35 U.S.C. §120

The present Application for Patent is a Continuation and claims priorityto patent application Ser. No. 10/177,132 entitled “Adaptive GainAdjustment Control” filed Jun. 20, 2002, now allowed, and assigned tothe assignee hereof and hereby expressly incorporated by referenceherein.

BACKGROUND

1. Field

The present invention relates generally to communications systems, andmore specifically, to systems and techniques for adaptively controllingthe gain of one or more channels in a communications system.

2. Background

Modern communications systems are designed for multiple user access to acommon communications medium. Numerous multiple-access techniques areknown in the art, such as time division multiple-access (TDMA),frequency division multiple-access (FDMA), space divisionmultiple-access, polarization division multiple-access, code divisionmultiple-access (CDMA), and other similar multi-access techniques. Themultiple-access concept is a channel allocation methodology which allowseach user to access a common communications medium without interferingwith others.

In multi-access communications systems, techniques to reduce mutualinterference between multiple users are often utilized to increase usercapacity. By way of example, power control techniques are currentlyemployed to limit the transmission power of each user to that necessaryto achieve a desired quality of service. This approach ensures that eachuser transmits only the minimum power necessary, but no higher, therebymaking the smallest contribution to the total noise seen by others.However, as user demands for multi-access capability increases,techniques to further reduce the transmission power of each user withoutcompromising the quality of service are needed.

SUMMARY

In one aspect of the present invention, a method of communicationsincludes transmitting a plurality of data groups to a receiver at afirst power level, retransmitting a first one of the data groups to thereceiver at a second power level lower than the first power level,providing feedback from the receiver relating to the retransmission ofthe first one of the data groups, and retransmitting a second one of thedata groups to the receiver at a third power level different from thesecond power level, the third power level being a function of thefeedback.

In another aspect of the present invention, computer-readable mediaembodying a program of instructions executable by a computer programperforms a method of communications, the method includes setting aplurality of data groups to a first power level for transmission to areceiver, setting a first one of the data groups to a second power levellower than the first power level for retransmission to the receiver,receiving feedback from the receiver relating to a retransmission of thefirst one of the data groups, and setting a second one of the datagroups to a third power level for retransmission to the receiver, thethird power level being a function of the feedback.

In yet another aspect of the present invention, an apparatus includes atransmitter, a buffer configured to provide a plurality of data groupsto the transmitter for initial transmission to a receiver, and provideat least first and second ones of the data groups to the transmitter forretransmission to the receiver, and a gain control configured to seteach of the data groups to a first power level for initial transmission,set the first one of the data groups to a second power level lower thanthe first power level, receive feedback from the receiver relating tothe first one of the data groups, and set the second one of the datagroups to a third power level as a function of the feedback.

In a further aspect of the present invention, an apparatus includes atransmitter, a buffer configured to provide a plurality of data groupsto the transmitter, and identify each of the data groups provided to thetransmitter as an initial transmission or retransmission to a receiver,and a gain control configured to set each of the data groups identifiedas an initial transmission to an initial power level, receive feedbackfrom the receiver related to each of the data groups identified as aretransmission, and adjust the power level for each of the data groupsidentified as a retransmission based on the feedback from the respectiveprevious retransmission.

In yet a further aspect of the present invention, an apparatus includesa transmitter, means for providing a plurality of data groups to thetransmitter for initial transmission to a receiver, means for providingat least first and second ones of the data groups to the transmitter forretransmission to the receiver, means for setting each of the datagroups to a first power level for initial transmission, means forsetting the first one of the data groups to a second power level lowerthan the first power level, means for receiving feedback from thereceiver relating to the first one of the data groups, and means forsetting the second one of the data groups to a third power level as afunction of the feedback.

It is understood that other embodiments of the present invention willbecome readily apparent to those skilled in the art from the followingdetailed description, wherein it is shown and described only exemplaryembodiments of the invention by way of illustration. As will berealized, the invention is capable of other and different embodimentsand its several details are capable of modification in various otherrespects, all without departing from the spirit and scope of the presentinvention. Accordingly, the drawings and detailed description are to beregarded as illustrative in nature and not as restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present invention are illustrated by way of example, andnot by way of limitation, in the accompanying drawings, wherein:

FIG. 1 is a conceptual overview of an exemplary CDMA communicationssystem;

FIG. 2 is a simplified functional block diagram of a subscriber stationconfigured to operate in a CDMA communications system;

FIG. 3 is a flow diagram illustrating an exemplary algorithm for a gaincontrol function in a subscriber station; and

FIG. 4 is a graphical illustration of an exemplary adaptivetraffic-pilot ratio used to implement the gain control function.

DETAILED DESCRIPTION

The detailed description set forth below in connection with the appendeddrawings is intended as a description of exemplary embodiments of thepresent invention and is not intended to represent the only embodimentsin which the present invention can be practiced. The term “exemplary”used throughout this description means “serving as an example, instance,or illustration,” and should not necessarily be construed as preferredor advantageous over other embodiments. The detailed descriptionincludes specific details for the purpose of providing a thoroughunderstanding of the present invention. However, it will be apparent tothose skilled in the art that the present invention may be practicedwithout these specific details. In some instances, well-known structuresand devices are shown in block diagram form in order to avoid obscuringthe concepts of the present invention.

In an exemplary communications system, power control techniques can beused to limit the power of each user to that necessary to achieve adesired quality of service. If the communications system supports packetdata services with retransmission capability for corrupted data, theretransmission power can be further limited by using the informationreceived from the corrupted data to decode the retransmitted data. Morespecifically, the soft decisions from the corrupted data can be softcombined with the retransmitted data to reduce the energy per bit (EbNt)required to maintain the desired quality of service. As a result, usercapacity of the system may be increased.

The application of these power control techniques can be illustratedwith reference to an exemplary CDMA communications system as shown inFIG. 1. CDMA is a modulation and multiple access technique based onspread-spectrum communications. In a CDMA communications system, a largenumber of signals share the same frequency spectrum. This is achieved bytransmitting each signal with a different code that modulates a carrier,and thereby, spreads the spectrum of the signal waveform. Thetransmitted signals are separated in the receiver by a demodulator thatuses a corresponding code to despread the desired signal's spectrum. Theundesired signals, whose codes do not match, are not despread inbandwidth and contribute only to noise.

Although various aspects of these power control techniques will bedescribed in the context of a CDMA communications system, those skilledin the art will appreciate that these techniques are equally applicableto various other communications environments. Accordingly, any referenceto a CDMA communications system is intended only to illustrate theinventive aspects of the present invention, with the understanding thatsuch inventive aspects have a wide range of applications.

Turning to FIG. 1, a base station controller 102 can be used to providean interface between a network 104 and all base stations dispersedthroughout a geographic area. The geographic area is divided intocoverage regions known as cells or sectors. A base station is generallyassigned to serve all subscriber stations in a coverage region. For easeof explanation, only one base station 106 is shown. A subscriber station108 may access the network 104, or communicate with other subscriberstations (not shown), through one or more base stations under control ofthe base station controller 102.

The exemplary CDMA communications system supports two-way communicationsbetween the base station 106 and the subscriber station 108.Transmissions from the base station 106 to the subscriber station 108are referred to as forward link transmissions, and transmissions fromthe subscriber 108 to the base station 106 are referred to as reverselink transmissions. The base station 106 typically controls the reverselink power of a reference or pilot signal transmitted from thesubscriber station 108 using various power control techniques well knownin the art. The subscriber station 108 also transmits traffic over thereverse link. The reverse link power of the traffic can be set by thesubscriber station 108 based on the power of the pilot signal using atraffic-pilot ratio. The traffic-pilot ratio may be set based on anynumber of parameters such as the carrier frequency, chip rate, datarate, modulation scheme, frame length, or any other parameters. In atleast one embodiment of the CDMA communications system, the base station106 can be configured to provide feedback to the subscriber station 108indicating whether the reverse link traffic can be successfully decoded.This can be accomplished by transmitting the reverse link traffic indata groups, typically known as frames, and sending an acknowledgement(ACK) response over the forward link for each frame that can besuccessfully decoded by the base station 106. For those frames thatcannot be successfully decoded, a negative acknowledgement (NACK)response can be sent to the subscriber station 108 over the forward linkrequesting a retransmission of that frame. Because the base station 106can use the information from the unsuccessfully decoded frame, thesubscriber station 108 can reduce the transmission power of the framebeing retransmitted by reducing the traffic-pilot ratio. In a manner tobe described in greater detail later, the level of power reduction forretransmitted frames can be adaptively adjusted to optimize performance.

FIG. 2 is a functional block diagram of an exemplary subscriber station.The subscriber station 108 includes a data buffer 202 which partitionsthe reverse link traffic into data groups for transmission to the basestation. The data groups can be data frames, or any other type of datagroups such as a data packets. The data buffer 202 includes a data queue203 and a frame synchronizer 204. The data queue 203 can be used tobuffer data from an external data source (not shown), and the framesynchronizer 204 can be used to control, the release of data framessequentially from the data queue 203 to an encoder 206. The encoder 206provides error correction coding and interleaving of the data withineach frame. The encoded frames can be provided to the modulator 208where they are spread with a Walsh cover and amplified with a gainsignal computed by a gain control 210. The Walsh covered frames can thenbe combined with other overhead signals, each having a unique Walshcode, spread with a long pseudo-random noise (PN) code generated by aunique user address mask, and quadrature modulated with short PN codesidentifying the base station. The quadrature modulated signal can thenbe provided to a transmitter 212 where it is upconverted, filtered andamplified for over the air transmission through an antenna 214 to thebase station.

Following the transmission of each data frame, a response may betransmitted from the base station to the subscriber station over theforward link indicating whether the data frame was successfully decoded.The response may be an ACK indicating that the data frame wassuccessfully decoded. Conversely, the response may be a NACK indicatingthat the data frame was corrupted and requesting a retransmission ofthat data frame. The response can be sent from the base station in aseparate transmission or accompanying the forward link traffic. Wherethe response is transmitted with the forward link traffic, the responsecan be time-division multiplexed, frequency-division multiplexed,code-division multiplexed, or multiplexed using any other scheme knownin the art. Alternatively, the response can be transmitted with theforward link pilot signal. This approach ensures timely delivery of theresponse to the subscriber station even when the forward link traffic isnot present. Typically, the response will be covered with a unique Walshfunction so that it can be combined with other forward linktransmissions before being quadrature modulated with the short PN codes.

The forward link transmission is received by the antenna 214 andprovided to a receiver 216. The receiver 216 filters, amplifies, anddownconverts the forward link transmission to a baseband signal. Thebaseband signal can be coupled to a demodulator 218 where it isquadrature demodulated with the short PN codes and decovered by theWalsh codes to separate the various signals. The forward link trafficcan then be despread using the long PN code and provided to a decoder220 for de-interleaving and decoding. The ACK or NACK response can becoupled from the demodulator 218 to the frame synchronizer 204. Theframe synchronizer 204 initiates the retransmission of the data frame inresponse to a NACK response by re-releasing the data frame from the dataqueue 203 after a predetermined retransmission delay. By way of example,if data frames 1, 2, 3, 4, 5, 6 and 7 are queued to be releasedsequentially from the data queue 203, and a NACK response is generatedfrom data frames 1, 3 and 4, then the frame synchronizer 204 will insertframe repeats in the sequence such that data frames 1, 2, 3, 1, 4, 3, 5,4, 6 and 7 are sequentially released from the data queue 203 if theretransmission delay is set for two data frames.

The transmission power for each data frame can be controlled by a gainsignal computed by the gain control 210 based on the traffic-pilotratio. The traffic-pilot ratio is typically predetermined during thecall set up based on any number of parameters such as the carrierfrequency, chip rate, data rate, modulation scheme, frame length, or anyother parameters. The gain signal applied to the data frames can becomputed by means well known in the art from the predeterminedtraffic-pilot ratio and the reverse link transmission power of the pilotsignal. In existing CDMA communications systems, the reverse linktransmission power of pilot signal is computed with two power controlloops: an open loop control and a closed loop control. The open loopcontrol is designed to control the reverse link transmission power ofthe pilot signal as a function of path loss, the effect of base stationloading, and environmentally induced phenomena such as fast fading andshadowing. The closed loop control is designed to correct the open loopestimate to achieve a desired signal-to-noise ratio. This can beachieved by measuring the reverse link power of the pilot signal at thebase station and providing feedback to the subscriber station to adjustthe reverse link transmission power for the pilot signal.

The gain applied to the data frames during retransmission can be reducedby reducing the traffic-pilot ratio. To optimize performance, thetraffic-pilot ratio should be reduced to the point where thetransmission power is limited to that necessary to successfully decodethe retransmitted frame at the base station using the soft decisions ofthe same frame previously transmitted. An adaptive algorithm can be usedto maintain an optimal traffic-pilot ratio for retransmission framesdespite changing data rates and environmental conditions. The adaptivealgorithm can be implemented to adjust the traffic-pilot ratio duringretransmission frames based on whether or not the previousretransmission frame was successfully decoded by the base station. Theprevious retransmission frame can be either the same frame, oralternatively, a retransmission of an entirely different data frame. Toillustrate this concept using the earlier example, if data frames 1, 2,3, 4, 5, 6 and 7 are queued to be released sequentially from the dataqueue 203, and a NACK response is generated from data frames 1, 3 and 4,then the frame synchronizer 204 will insert frame repeats in thesequence such that data frames 1, 2, 3, 1, 4, 3, 5, 4, 6 and 7 aresequentially released from the data queue 202. In this case, thetraffic-pilot ratio used to compute the gain signal for theretransmission of frame 3 will be based on the feedback from the basestation for the retransmission of frame 1.

A flag 204 a set by the frame synchronizer 204 can be used by the gaincontrol 210 to identify the retransmission frames. If the framesynchronizer 204 releases a data frame from the data queue 203 forinitial transmission, the flag 204 a is cleared, and the gain control210 uses the predetermined traffic-pilot ratio to compute the gainsignal. Conversely, if the frame synchronizer 204 releases a data framefrom the data queue 203 for retransmission, the flag 204 a is set, andthe gain control 210 adjusts the traffic-pilot ratio to some level belowthe predetermined level, computes the gain signal applied to the dataframe in the modulator 208 based on the adjusted traffic-pilot ratio,and listens for feedback from the base station for the retransmitteddata frame. The feedback 218 a can be provided to the gain control 210from the demodulator 218. When the next retransmission frame is releasedfrom the data queue 203, the feedback for the previous retransmissionframe can be used to adjust the traffic-pilot ratio to compute a newgain signal.

Various algorithms can be implemented by the gain control depending onthe particular application and overall design requirements. FIG. 3 is aflow diagram illustrating an exemplary algorithm. In step 302, apredetermined traffic-pilot ratio is established based on variousparameters such as the carrier frequency, chip rate, data rate,modulation scheme, frame length, or any other parameters. This istypically done during call set up. In step 304, the flag from the framesynchronizer is checked to determine whether the data frame releasedfrom the data queue is a retransmission frame. If the data frame is nota retransmission frame, the traffic-pilot ratio is set to thepredetermined value to compute the gain signal in step 306. Conversely,if the data frame released from the data queue is a retransmissionframe, then a determination is made as to whether the data frame is thefirst retransmission frame of the call in step 308. If the data frame isthe first retransmission of the call, then the traffic-pilot ratio isset to a minimum value to compute the gain signal in step 310.

Assuming that the data frame is not the first retransmission of thecall, then a determination is made as to whether the previousretransmission frame was successfully decoded by the base station instep 312. If the previous retransmission frame was successfully decoded,then the traffic-pilot ratio for the current retransmission frame isreduced in step 314. The magnitude of the traffic-pilot ratio reductionis application dependent and those skilled in the art will be readilyable to determine the appropriate magnitude based on the overall designparameters. The reduced traffic-pilot ratio is then compared with theminimum value in step 316. If the reduced traffic-pilot is greater thanor equal to the minimum value, then the reduced traffic-pilot ratio isused to compute the gain signal in step 318. Conversely, if the reducedtraffic-pilot ratio is below the minimum value, then the traffic-pilotratio is set to the minimum value and the gain signal is computed at theminimum value in step 320.

Assuming that the previous retransmission frame was not successfullydecoded at the base station, then the traffic-pilot ratio for thecurrent retransmission frame is increased in step 322. The magnitude ofthe traffic-pilot ratio increase is application dependent and thoseskilled in the art will be readily able to determine the appropriatemagnitude based on the overall design parameters. The increasedtraffic-pilot ratio is then compared with a maximum value in step 324.If the increased traffic-pilot is less than or equal to the maximumvalue, then the increased traffic-pilot ratio is used to compute thegain signal in step 326. Conversely, if the increased traffic-pilotratio is above the maximum value, then the traffic-pilot ratio is set tothe maximum value and the gain signal is computed at the maximum valuein step 328.

An exemplary application of the algorithm can be illustrated using theearlier example with data frames 1, 2, 3, 4, 5, 6 and 7 queued to bereleased sequentially from the data queue, and a NACK response generatedfrom data frames 1, 3 and 4, resulting in data frames 1, 2, 3, 1, 4, 3,5, 4, 6 and 7 being sequentially released from the data queue. For thepurposes of explanation, the predetermined traffic-pilot ratio is equalto the maximum traffic-pilot ratio which is equal to 5 dB. The magnitudeof any increase in the traffic-pilot ratio will be equal to ½ of themagnitude in dB between the traffic-pilot ratio for the previousretransmission frame and the maximum traffic-pilot ratio. In addition,the minimum traffic-pilot ratio is equal to 1 dB, and the magnitude ofany reduction in the traffic-pilot ratio is equal to ½ the magnitude indB between the traffic-pilot ratio for the previous retransmission frameand the minimum traffic-pilot ratio.

A graphical illustration of the adaptive traffic-pilot ratio under theseconditions is shown in FIG. 4. The initial transmission of data frames1, 2, and 3 would be transmitted with a traffic-pilot ratio of 5 dB. Theretransmission of data frame 1, being the first retransmission for thecall, would be transmitted at the minimum traffic-pilot ratio, i.e., 1dB. The initial transmission of frame 4 following the retransmission offrame 1 would be at the predetermined traffic-pilot ratio, i.e., 5 dB.The traffic-pilot ratio used for the retransmission of frame 3 woulddepend on whether the retransmission of frame 1 was successfully decodedat the base station. If the retransmission of frame 1 was notsuccessfully decoded, then the traffic-pilot ratio for theretransmission of frame 3 would be adjusted to 3 dB as shown in FIG. 4,i.e., half the magnitude between the traffic-pilot ratio for theretransmission of frame 1 and the maximum value. Conversely, if theretransmission of frame 1 was successfully decoded at the base station,then the traffic-pilot ratio for the retransmission of frame 3 would beadjusted to 1 dB. Either way, the initial transmission of frame 5following the retransmission of frame 3 would be at the predeterminedtraffic-pilot ratio, i.e., 5 dB.

The retransmission of frame 4 would depend on whether the retransmissionof frame 3 was successfully decoded at the base station. Assuming thatthe retransmission of frame 3 occurred with a traffic-pilot ratio of 3dB and was successfully decoded at the base station, then thetraffic-pilot ratio for the retransmission of frame 4 would be adjustedto 2 dB as shown in FIG. 4, i.e., half the magnitude between thetraffic-pilot ratio for the retransmission of frame 3 and the minimumvalue. Assuming that the retransmission of frame occurred with atraffic-pilot ratio of 3 dB and was not successfully decoded at the basestation, then the traffic-pilot ratio for the retransmission of frame 4would be adjusted to 4 dB, i.e., half the magnitude between thetraffic-pilot ratio for the retransmission of frame 3 and the maximumvalue. Either way, the initial transmission of frames 6 and 7 followingthe retransmission of frame 4 would be at the predeterminedtraffic-pilot ratio, i.e., 5 dB.

The various illustrative logical blocks, modules, and circuits describedin connection with the embodiments disclosed herein may be implementedor performed with a general purpose processor, a digital signalprocessor (DSP), an application specific integrated circuit (ASIC), afield programmable gate array (FPGA) or other programmable logic device,discrete gate or transistor logic, discrete hardware components, or anycombination thereof designed to perform the functions described herein.A general-purpose processor may be a microprocessor, but in thealternative, the processor may be any conventional processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices, e.g., a combinationof a DSP and a microprocessor, a plurality of microprocessors, one ormore microprocessors in conjunction with a DSP core, or any other suchconfiguration.

The methods or algorithms described in connection with the embodimentsdisclosed herein may be embodied directly in hardware, in a softwaremodule executed by a processor, or in a combination of the two. Asoftware module may reside in RAM memory, flash memory, ROM memory,EPROM memory, EEPROM memory, registers, hard disk, a removable disk, aCD-ROM, or any other form of storage medium known in the art. Anexemplary storage medium is coupled to the processor such the processorcan read information from, and write information to, the storage medium.In the alternative, the storage medium may be integral to the processor.The processor and the storage medium may reside in an ASIC. The ASIC mayreside in a user terminal. In the alternative, the processor and thestorage medium may reside as discrete components in a user terminal.

The previous description of the disclosed embodiments is provided toenable any person skilled in the art to make or use the presentinvention. Various modifications to these embodiments will be readilyapparent to those skilled in the art, and the generic principles definedherein may be applied to other embodiments without departing from thespirit or scope of the invention. Thus, the present invention is notintended to be limited to the embodiments shown herein but is to beaccorded the widest scope consistent with the principles and novelfeatures disclosed herein.

1. A method of communications, comprising: transmitting a plurality ofdata groups to a receiver at a first power level; decoding the pluralityof data groups by the receiver; and retransmitting one of the datagroups at a second power level lower than the first power level if theone of the data groups is unsuccessfully decoded by the receiver.
 2. Themethod of claim 1 further comprising retransmitting another of the datagroups at third power level different from the second power level if theanother of the data groups is unsuccessfully decoded by the receiver. 3.The method of claim 2 further including adjusting the third power levelas a function of the second power level.
 4. The method of claim 3further including: lowering the third power level relative to the secondpower level if the one of the data groups is successfully decoded; andincreasing the third power level relative to the second power level ifthe one of the data groups is unsuccessfully decoded.
 5. A method ofcommunications, comprising: transmitting a plurality of data groups to areceiver at a first power level; retransmitting a first one of the datagroups to the receiver at a second power level lower than the firstpower level; providing feedback from the receiver relating to theretransmission of the first one of the data groups; and retransmitting asecond one of the data groups to the receiver at a third power leveldifferent from the second power level, the third power level being afunction of the feedback.
 6. The method of claim 5 wherein the thirdpower level is set relative to the second power level as a function ofthe feedback.
 7. The method of claim 5 wherein each of the data groupscomprises a data frame.
 8. The method of claim 5 wherein the third powerlevel is less than the first power level.
 9. The method of claim 5further comprising encoding each of the data groups, and wherein thefeedback indicates whether the retransmission of the first one of thedata groups was successfully decoded by the receiver.
 10. The method ofclaim 9 wherein the third power level is set higher than the secondpower level if the feedback indicates that the retransmission of thefirst one of the data groups was not successfully decoded by thereceiver, and the third power level is set lower than the second powerlevel if the feedback indicates that the retransmission of the first oneof the data groups was successfully decoded by the receiver.
 11. Themethod of claim 10 wherein the third power level is set half-way betweenthe first power level and the second power level if the feedbackindicates that the retransmission of the first one of the data groupswas not successfully decoded by the receiver, and the third power levelis set half-way between a minimum power level and the second power levelif the feedback indicates that the retransmission of the first one ofthe data groups was successfully decoded by the receiver, the minimumpower level being less than the second power level.
 12. The method ofclaim 5 further comprising computing a reference power level fortransmitting a reference signal with each of the data groups, computinga first power ratio as function of a parameter, setting the first powerlevel as a function of the reference power level and the first powerratio, deriving a second power ratio, setting of the second power levelas a function of the reference power level and the second power ratio,deriving a third power ratio as a function of the feedback, and settingthe third power level as a function of the reference power level and thepower ratio.
 13. The method of claim 12 wherein the third power ratio isset relative to the second power ratio as a function of the feedback.14. The method of claim 12 wherein the first power ratio is defined asthe first power level divided by the reference power level, the secondpower ratio is defined as the second power level divided by thereference power level, and the third power ratio is defined as the thirdpower level divided by the reference power level.
 15. The method ofclaim 14 wherein the third power ratio is less than the first powerratio.
 16. The method of claim 12 further comprising encoding each ofthe data groups, and wherein the feedback indicates whether theretransmission of the first one of the data groups was successfullydecoded by the receiver.
 17. The method of claim 16 wherein the firstpower ratio is defined as the first power level divided by the referencepower level, the second power ratio is defined as the second power leveldivided by the reference power level, and the third power ratio isdefined as the third power level divided by the reference power level,the third power ratio being set higher than the second power ratio ifthe feedback indicates that the retransmission of the first one of thedata groups was not successfully decoded by the receiver, and thirdpower ratio being set lower than the second power ratio if the feedbackindicates that the retransmission of the first one of the data groupswas successfully decoded by the receiver.
 18. The method of claim 17wherein the third power ratio is set half-way between the first powerratio and the second power ratio if the feedback indicates that theretransmission of the first one of the data groups was not successfullydecoded by the receiver, and the third power ratio is set half-waybetween a minimum power ratio and the second power ratio if the feedbackindicates that the retransmission of the first one of the data groupswas successfully decoded by the receiver, the minimum power ratio beingless than the second power ratio.
 19. Computer-readable media embodyinga program of instructions executable by a computer program to perform amethod of communications, the method comprising: transmitting aplurality of data groups to a receiver at a first power level; decodingthe plurality of data groups by the receiver; and retransmitting one ofthe data groups at a second power level lower than the first power levelif the one of the data groups is unsuccessfully decoded by the receiver.20. The computer-readable media of claim 19 wherein the method furthercomprising retransmitting another of the data groups at third powerlevel different from the second power level if the another of the datagroups is unsuccessfully decoded by the receiver.
 21. Thecomputer-readable media of claim 20 wherein the method further includingadjusting the third power level as a function of the second power level.22. The computer-readable media of claim 21 wherein the method furtherincluding: lowering the third power level relative to the second powerlevel if the one of the data groups is successfully decoded; andincreasing the third power level relative to the second power level ifthe one of the data groups is unsuccessfully decoded.
 23. An apparatus,comprising: a transmitter; a buffer configured to provide a plurality ofdata groups to the transmitter for initial transmission to a receiver,and provide at least first and second ones of the data groups to thetransmitter for retransmission to the receiver; and a gain controlconfigured to set each of the data groups to a first power level forinitial transmission, set the first one of the data groups to a secondpower level lower than the first power level, receive feedback from thereceiver relating to the first one of the data groups, and set thesecond one of the data groups to a third power level as a function ofthe feedback.
 24. The apparatus of claim 23 wherein the gain control isfurther configured to set the third power level relative to the secondpower level as a function of the feedback.
 25. The apparatus of claim 23wherein each of the data groups comprises a data frame.
 26. Theapparatus of claim 23 wherein the gain control is further configured toset the third power level lower than the first power level.
 27. Theapparatus of claim 23 further comprising an encoder configured to encodeeach of the data groups from the buffer before transmission, and whereinthe feedback indicates whether the retransmission of the first one ofthe data groups was successfully decoded by the receiver.
 28. Theapparatus of claim 27 wherein the gain control is further configured toset the third power level higher than the second power level if thefeedback indicates that the retransmission of the first one of the datagroups was not successfully decoded by the receiver, and set the thirdpower level lower than the second power level if the feedback indicatesthat the retransmission of the first one of the data groups wassuccessfully decoded by the receiver.
 29. The apparatus of claim 28wherein the gain control is further configured to set the third powerlevel half-way between the first power level and the second power levelif the feedback indicates that the retransmission of the first one ofthe data groups was not successfully decoded by the receiver, and setthe third power level half-way between a minimum power level and thesecond power level if the feedback indicates that the retransmission ofthe first one of the data groups was successfully decoded by thereceiver, the minimum power level being less than the second powerlevel.
 30. The apparatus of claim 23 further comprising a referencesignal generator configured to generate a reference signal and provideit to the transmitter for transmission with each of the data groups, thereference signal having a reference power level, and wherein the gaincontrol is further configured to compute a first power ratio as functionof a parameter, set the first power level as a function of the referencepower level and the first power ratio, derive a second power ratio, setthe second power level as a function of the reference power level andthe second power ratio, derive a third power ratio as a function of thefeedback, and set the third power level as a function of the referencepower level and the power ratio.
 31. The apparatus of claim 30 whereingain control is further configured to set the third power ratio relativeto the second power ratio as a function of the feedback.
 32. Theapparatus of claim 30 wherein the first power ratio is defined as thefirst power level divided by the reference power level, the second powerratio is defined as the second power level divided by the referencepower level, and the third power ratio is defined as the third powerlevel divided by the reference power level.
 33. The apparatus of claim32 wherein the gain control is further configured to set the third powerratio lower than the first power ratio.
 34. The apparatus of claim 30further comprising an encoder configured to encode each of the datagroups from the buffer before transmission, and wherein the feedbackindicates whether the retransmission of the first one of the data groupswas successfully decoded by the receiver.
 35. The apparatus of claim 34wherein the first power ratio is defined as the first power leveldivided by the reference power level, the second power ratio is definedas the second power level divided by the reference power level, and thethird power ratio is defined as the third power level divided by thereference power level, and wherein the gain control is furtherconfigured to set the third power ratio higher than the second powerratio if the feedback indicates that the retransmission of the first oneof the data groups was not successfully decoded by the receiver, and setthe third power ratio lower than the second power ratio if the feedbackindicates that the retransmission of the first one of the data groupswas successfully decoded by the receiver.
 36. The apparatus of claim 35wherein the gain control is further configured to set the third powerratio half-way between the first power ratio and the second power ratioif the feedback indicates that the retransmission of the first one ofthe data groups was not successfully decoded by the receiver, and setthe third power ratio half-way between a minimum power ratio and thesecond power ratio if the feedback indicates that the retransmission ofthe first one of the data groups was successfully decoded by thereceiver, the minimum power ratio being less than the second powerratio.
 37. An apparatus, comprising: a transmitter; a buffer configuredto provide a plurality of data groups to the transmitter, and identifywhether each of the data groups provided to the transmitter is aninitial transmission or retransmission to a receiver; and a gain controlconfigured to set each of the data groups identified as an initialtransmission to an initial power level, receive feedback from thereceiver related to each of the data groups identified as aretransmission, and adjust the power level for each of the data groupsidentified as a retransmission based on the feedback from the respectiveprevious retransmission.
 38. The apparatus of claim 37 wherein the gaincontrol is further configured to adjust the power level for each of thedata groups identified as a retransmission based on both the feedbackfor the respective previous retransmission and the adjusted power levelfor that previous retransmission.
 39. The apparatus of claim 38 whereineach of the data groups comprises a data frame.
 40. The apparatus ofclaim 37 wherein the adjusted power level is less than the initial powerlevel.
 41. The apparatus of claim 37 further comprising an encoderconfigured to encode each of the data groups from the buffer beforetransmission, and wherein the feedback indicates whether theretransmission of each of the data groups was successfully decoded bythe receiver.
 42. The apparatus of claim 41 wherein the gain control isfurther configured to adjust the power level upward relative to theadjusted power level for the previous retransmission if the feedbackindicates that the previous retransmission was not successfully decodedby the receiver, and adjust the power level downward relative to theadjusted power level for the previous retransmission if the feedbackindicates that the previous retransmission was successfully decoded bythe receiver.
 43. The apparatus of claim 42 wherein the adjusted powerlevel is less than the initial power level, and wherein the gain controlis further configured to adjust the power level half-way between theinitial power level and the adjusted power level for the previousretransmission if the feedback indicates that the previousretransmission was not successfully decoded by the receiver, and adjustthe power level half-way between a minimum power level and the adjustedpower level for the previous retransmission if the feedback indicatesthat the previous retransmission was successfully decoded by thereceiver, the minimum power level being less than the adjusted powerlevel for the previous retransmission.
 44. The apparatus of claim 37further comprising a reference signal generator configured to generate areference signal and provide it to the transmitter for transmission witheach of the data groups, the reference signal having a reference powerlevel, and wherein the gain control is further configured to compute aninitial power ratio as function of a parameter, set the initial powerlevel as a function of the reference power level and the initial powerratio, adjust the power ratio as a function of the feedback for theprevious retransmission, and adjust the power level as a function of thereference power level and the adjusted power ratio.
 45. The apparatus ofclaim 44 wherein gain control is further configured to adjust the powerratio as a function of both the feedback for the previous retransmissionand the adjusted power ratio for that retransmission.
 46. The apparatusof claim 44 wherein the initial power ratio is defined as the initialpower level divided by the reference power level, and the adjusted powerratio is defined as the adjusted power level divided by the referencepower level.
 47. The apparatus of claim 46 wherein the gain control isfurther configured to adjust the power level lower than the initialpower ratio.
 48. The apparatus of claim 44 further comprising an encoderconfigured to encode each of the data groups from the buffer beforetransmission, and wherein the feedback indicates whether the respectiveretransmission was successfully decoded by the receiver.
 49. Theapparatus of claim 48 wherein the initial power ratio is defined as theinitial power level divided by the reference power level, and theadjusted power ratio is defined as the adjusted power level divided bythe reference power level, and wherein the gain control is furtherconfigured to adjust the power ratio upward with respect to the adjustedpower ratio for the previous retransmission if the feedback indicatesthat the previous retransmission was not successfully decoded by thereceiver, and adjust the power ratio downward with respect to theadjusted power ratio for the previous transmission if the feedbackindicates that the previous retransmission was successfully decoded bythe receiver.
 50. The apparatus of claim 49 wherein the adjusted powerlevel is less than the initial power level, and wherein the gain controlis further configured to adjust the power level half-way between theinitial power level and the adjusted power level for the previousretransmission if the feedback indicates that the previousretransmission was not successfully decoded by the receiver, and adjustthe power level half-way between a minimum power level and the adjustedpower level for the previous retransmission if the feedback indicatesthat the previous retransmission was successfully decoded by thereceiver, the minimum power level being less than the adjusted powerlevel for the previous retransmission.
 51. An apparatus forcommunications, comprising: means for transmitting a plurality of datagroups to a receiver at a first power level; means for receivingfeedback from the receiver; and means for retransmitting one of the datagroups at a second power level lower than the first power level if theone of the data groups is unsuccessfully decoded by the receiver. 52.The apparatus of claim 51 further comprising means for retransmittinganother of the data groups at third power level different from thesecond power level if the another of the data groups is unsuccessfullydecoded by the receiver.
 53. The apparatus of claim 52 further includingmeans for adjusting the third power level as a function of the secondpower level.
 54. The apparatus of claim 53 further including: means forlowering the third power level relative to the second power level if theone of the data groups is successfully decoded; and means for increasingthe third power level relative to the second power level if the one ofthe data groups is unsuccessfully decoded.
 55. An apparatus, comprising:a transmitter; means for providing a plurality of data groups to thetransmitter for initial transmission to a receiver; means for providingat least first and second ones of the data groups to the transmitter forretransmission to the receiver; means for setting each of the datagroups to a first power level for initial transmission; means forsetting the first one of the data groups to a second power level lowerthan the first power level; means for receiving feedback from thereceiver relating to the first one of the data groups; and means forsetting the second one of the data groups to a third power level as afunction of the feedback.
 56. The apparatus of claim 55 wherein thethird power level is set relative to the second power level as afunction of the feedback.
 57. The apparatus of claim 55 wherein each ofthe data groups comprises a data frame.
 58. The apparatus of claim 55wherein the third power level is set below the first power level. 59.The apparatus of claim 55 further comprising means for encoding each ofthe data groups before transmission, and wherein the feedback indicateswhether the retransmission of the first one of the data groups wassuccessfully decoded by the receiver.
 60. The apparatus of claim 59wherein the third power level is set above the second power level if thefeedback indicates that the retransmission of the first one of the datagroups was not successfully decoded by the receiver, and the third powerlevel is set lower than the second power level if the feedback indicatesthat the retransmission of the first one of the data groups wassuccessfully decoded by the receiver.
 61. The apparatus of claim 60wherein the third power level is set half-way between the first powerlevel and the second power level if the feedback indicates that theretransmission of the first one of the data groups was not successfullydecoded by the receiver, and the third power level is set half-waybetween a minimum power level and the second power level if the feedbackindicates that the retransmission of the first one of the data groupswas successfully decoded by the receiver, the minimum power level beingless than the second power level.
 62. The apparatus of claim 55 furthercomprising means for generating a reference signal having a referencepower level, means for providing the reference signal to the transmitterfor transmission with each of the data groups, and means for computing afirst power ratio as function of a parameter, wherein the first powerlevel is set as a function of the reference power level and the firstpower ratio, the apparatus further comprising means for deriving secondand third power ratios, the third power ratio being a function of thefeedback, and wherein the second power level is set as a function of thereference power level and the second power ratio, and the third powerratio is set as a function of the reference power level and the powerratio.
 63. The apparatus of claim 62 wherein the third power ratio isset relative to the second power ratio as a function of the feedback.64. The apparatus of claim 62 wherein the first power ratio is definedas the first power level divided by the reference power level, thesecond power ratio is defined as the second power level divided by thereference power level, and the third power ratio is defined as the thirdpower level divided by the reference power level.
 65. The apparatus ofclaim 64 wherein the third power ratio is set lower than the first powerratio.
 66. The apparatus of claim 62 further comprising means forencoding each of the data groups before transmission, and wherein thefeedback indicates whether the retransmission of the first one of thedata groups was successfully decoded by the receiver.
 67. The apparatusof claim 66 wherein the first power ratio is defined as the first powerlevel divided by the reference power level, the second power ratio isdefined as the second power level divided by the reference power level,and the third power ratio is defined as the third power level divided bythe reference power level, and wherein the third power ratio is sethigher than the second power ratio if the feedback indicates that theretransmission of the first one of the data groups was not successfullydecoded by the receiver, and the third power ratio is set lower than thesecond power ratio if the feedback indicates that the retransmission ofthe first one of the data groups was successfully decoded by thereceiver.
 68. The apparatus of claim 67 wherein the third power ratio isset half-way between the first power ratio and the second power ratio ifthe feedback indicates that the retransmission of the first one of thedata groups was not successfully decoded by the receiver, and set thethird power ratio half-way between a minimum power ratio and the secondpower ratio if the feedback indicates that the retransmission of thefirst one of the data groups was successfully decoded by the receiver,the minimum power ratio being less than the second power ratio.